1. Field of the Invention
The present invention relates to an exhaust emission purification device having a catalyst body formed of a sintered catalyst material.
2. Description of the Background Art
The German Patent Application DE 102 51 624 A1 illustrates an exhaust gas purification device for vehicles, and which includes a tubular housing and a honeycomb-shaped catalyst body. The honeycomb-shaped catalyst body includes a plurality of flow channels extending from an intake side to a discharge side of the catalyst body to thereby allow an exhaust gas to pass through the catalyst body. Further, the flow channels are formed via a plurality of staggered sheet metal layers. The honeycomb-shaped catalyst body also includes a wash-coat layer (carrier layer), which forms a very large surface and on which a catalyst material such as platinum, rhodium or palladium is dispersed. In addition, the catalyst material is a catalytically active material that reacts with the exhaust gas to thereby reduce noxious substances such as carbon monoxide, unsaturated hydrocarbons, and nitrate monoxide contained in the exhaust gas. Also, the wash-coat layer expedites an oxidation process of the exhaust gas due to its ability to store oxygen.
However, this type of exhaust gas purification device is disadvantageous, because a catalyst material coating layer is always required, irregardless of the material used to make the catalyst body. Further, it is difficult to ensure that the coating layer is even, both in thickness and distribution. In addition, the coating layer tends to flake off in some areas of the catalyst body, which diminishes the catalytic effect. Also, particles present in the exhaust gas form within fine pores of the coating layer thereby sealing off that portion of the coating layer, which reduces the effectiveness of the coating layer.
In addition, the German Patent Application DE 198 32 625 C2 illustrates a method for making a stacked reactor for producing hydrogen from hydrocarbons. In this method, a catalyst material is used make catalyst disks, which are stacked on top of each other. However, this type of stacked reactor is not suitable for use in an exhaust gas purification device for vehicles. Further, the German Patent Publication DE 199 35 276 A1 illustrates a method of producing components by mixing a metal powder mass with a binder. In this method, a preform is made using a metal injection molding process. Subsequently, about 75 percent of a binder is removed from the produced molded component.